1. Field of the Invention
The present invention relates to a zero insertion force electrical connector assembly for making edge connection with printed circuit boards and the like.
2. Brief Description of the Prior Art
Conventional printed circuit wiring techniques have given rise to the adoption of special electrical connector devices, one specie of which may be referred to as edge connectors. Edge connectors generally comprise a support frame or housing with an opening of one sort or another for receiving a portion, or edge, of the associated printed circuit board therein. The connector assembly customarily includes a plurality of terminals arranged in some manner such that upon insertion of the printed circuit board, electrical continuity is effectively established between the connector terminals and the conducting tabs or strips defined in the board. Usually these terminals are spring-loaded or otherwise resiliently pressed against the printed circuit board being inserted in the connector housing so that an appropriate contact force is developed to hold the board and connector togeter as a composite unit. Further, the force developed must be of such magnitude to ensure that a sufficiently low resistance connection is established and maintained between th printed circuit board conductive strips or tabs and the resilient terminals of the connector assembly itself.
As a consequence of this relatively high contact pressure, a wear problem more often than not develops regarding the contact surfaces on the terminal and/or the associated printed circuit board conductive surfaces. Moreover, it is often difficult to insert and properly align the printed circuit board within the connector housing in the face of this inherent clamping force. The board frequently becomes wedged in a sidewise position and considerable effort and time is often required to effect its removal and reinsertion in the required correct alignment.
Still another difficulty is frequently encountered due to the lack of uniformity in the thickness dimensions of such printed circuit boards. An increase in the thickness of such boards will result in still higher contact or clamping forces exerted and further compound problems. A decrease in the board thickness past a given point simply will not generate the required low resistance connection.
U.S. Pat. No. 3,795,888, discloses an edge connector of the general type above described. However, the configuration disclosed therein does not provide a stable relationship between the connector assembly and the printed circuit board. The reason for that is because the printed circuit board is cantilevered outwardly from the connector assembly and offers no resistance to a board pull out force.
U.S. Pat. Nos. 3,701,071 and 3,848,952 disclose edge connectors which offer a greater stability than the connector disclosed in U.S. Pat. No. 3,795,888. The reason for this additional stability is due to separate board supporting member which can prove to be expensive, as well as cumbersome.
In addition to the above problems, there is also the desirability of stacking th connectors, i.e., the ability of mounting a plurality of connector assemblies along an edge in very close proximity to one another so that the progression distance between terminals of adjacent connector assemblies is constant. None of the edge connector assemblies disclosed in the above identified patents offers or discloses any stackability feature.